Lets make some assumptions: We have an isolated system, the projectile is launched from ground level, none of the initial energy from the launch is converted into internal energy, it doesn't rotate, we ignore the collision with the ground, and there are no external forces acting on the projectile/launcher.
Dependent on the angle of launch, some of the initial KE is converted into a form of potential energy: mgh. The greater the angle, the more KE is getting converted into gravitational potential energy on the arc upwards, does the total energy of the system change in this case?
Imagine it is just pointed up at 90 degrees, so that at the peak of the flight when the KE is 0, all the energy is potential. When it returns to ground level and gravitational potential energy is 0, KE is maxed. What can you say about the energy dependent on angle of launch? Then look at an angle of 0 so that the projectile rolls across the ground, without external forces acting on the projectile, all the energy in this case is kinetic. Is this initial and final energy a greater value than the energy of the 90 degree launch?
I think something along these lines is what the questions trying to get you to think about, maybe I'm wrong.